Examples

But when a new enemy called Parallax threatens to destroy the balance of power in the Universe, their fate and the fate of Earth lies in the hands of their newest recruit, the first human evert selected: Hal Jordan.

Briefly, the process is as follows: 2 slugs climb up a vertical surface, one leading the other; then they start circling each other; then they intertwine and suspend themselves by a thick strand of mucus; their penises evert and they too intertwine forming a bell-shaped structure at their lower end; the exchange of spermatophores presumably takes place within the bell; following this, the slugs abruptly separate and move away.